Arsenic in Minnesota's water: How worried should we be?

Just a week ago, we shared a report from the Center for Public Integrity showing that Minnesota has a serious problem involving arsenic in its groundwater, with many areas reporting levels much higher than the EPA's limit of 10 parts per billion.

If you look at the map accompanying the center's report, the situation in Minnesota looks dire, far worse than any other state. The map shows much of Minnesota covered in black dots, representing areas where arsenic levels are above 50 parts per billion, five times the EPA limit.

So should we be panicking? Well, Minnesota's groundwater arsenic problem is bad, but it's not as bad as you might think, especially compared with the rest of the country. Mindy Erickson, a hydrologist with the Minnesota Water Science Center, says the reason Minnesota looks so much worse than every other state has more to do with the quality of Minnesota's water testing than the quality of its water.

For years, Erickson said, only public wells had to be tested for arsenic, with private wells exempted. But in 2008, that all changed.

"Our state health department recognized [arsenic] as a huge health problem many years ago and worked for a decade so that in 2008, rules made it so every newly constructed well required testing," Erickson says. So with all those privately tested wells now added to the mix, Erickson says, it makes Minnesota look a whole lot worse than the 48 states who don't require private wells to be tested (Texas also tests its private wells).

That's not to say that arsenic isn't a problem. It still is, especially in Minnesota. A 2001 study of selected private wells in western Minnesota found that about 35 percent of wells had arsenic levels above 20 parts per billion. The state now believes that about 10 percent of all wells in the state have arsenic levels above the EPA limit.

Minnesota is especially at risk due to its history. Thousands of years ago, glaciers carried layers of rocks from Canada through the Midwest, dropping off arsenic-rich sediments in Minnesota. Those sediments are now in the spots where many Minnesota residents, especially in central and Western Minnesota, drill their private wells. And the health effects of that can be serious.

"Well, there's a long list of health effects to be concerned about," said Joseph Graziano, a Columbia University professor specializing in arsenic exposure. Among those effects, Graziano says, are skin cancer, bladder cancer, lung cancer, and cardiovascular disease.

Graziano also pointed to a new study by his team in Maine, a state with a similar arsenic problem to Minnesota. The study showed that on average, elementary school students whose drinking water had 5 parts per billion or more of arsenic in it had IQ levels that were 5 to 6 points lower than other students.

"No one should hang their hats on a single study, but it looks like, just like with lead, very low levels (of arsenic) can be harmful," Graziano said.

But Erickson says that preventing those sorts of problems can be a relatively simple process. If you drink from a public source of water, Erickson says, you're most likely fine, as those are already tested by the state. But for those drinking from private wells, especially older ones, make sure to get your water tested, because you could be at risk.